Metered mechanical tappet

ABSTRACT

A mechanical metering tappet which controls the oil pressure in the hollow push rod for supplying oil to overhead oiling systems of internal combustion engines by restricting the flow of the oil to the push rod. In one embodiment, this is accomplished by utilizing the diametral clearance of the push rod seat within its supporting cavity as the passageway for the oil from the crankcase to the reservoir. In another embodiment, the diametral clearance of the push rod seat is utilized to permit flow of oil but a metering disc used in conjunction with a specially configurated bottom surface of the seat provides the metering function. In both embodiments, the oil inlet hole in the tappet body is positioned above the tappet support shoulder for the push rod seat.

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54 METERED MECHANICAL TAPPET Primary ExaminerAl Lawrence Smith 9 Chin, 4 Drawing Figs Attorney-Price, Heneveld, Huizenga & Cooper ABSTRACT: A mechanical metering tappet which controls F01] 1/14, the oil pressure in the hollow push rod for supplying oil to F0lm9/l0 overhead oiling systems of internal combustion engines by 123/9035, restricting the flow of the oil to the push rod. In one embodiment, this is accomplished by utilizing the diametral clearance of the push rod seat within its supporting cavity as the Field of 90.48, 90.55, 90.56, 90.59, 90.63; 184/6, 6 T

[56] References Cited UNITED STATES PATENTS passageway for the oil from the crankcase to the reservoir. In

another embodiment. the diametral clearance of the push rod seat is utilized to permit flow of oil but a metering disc used in conjunction with a specially configurated bottom surface of the seat provides the metering function. In both embodiments, the oil inlet hole in the tappet body is positioned above the tappet support shoulder for the push rod seat.

5 Haa 0 9 9 /O/ 393 nNu 2 nh me gun ih [C010 BSCA 9469 6666 9999 1111 I/l/ 0026 111 i lu MM 5 a aurllllgnl METERED MECHANICAL TAPPET BACKGROUND OF THE INVENTION Although mechanical tappets do not require hydraulic fluid for their operation in contrast with the hydraulic tappets, nevertheless in an overhead oiling system oil must be supplied to the rocker arms for lubrication thereof. A conventional way of accomplishing this is by supplying the oil through the push rod. Most prior constructions so utilizing the push rod have resulted in improper control of the flow of the oil through the push rod, and attempts to meter the flow have not overcome come the problem of blockage due to foreign particles while at the same time not wasting oil by utilizing too much metering.

Satisfactory metering devices havebeen developed for use in mechanical tappets. However, to my knowledge these all involve high-pressure oil flow into the oil reservoir below the push rod seat, thus tending to result in an excess of oil flow on the base circle of the cam member for the tappet.

SUMMARY OF THE INVENTION The invention provides a metering mechanical tappet which is constructed so as to supply only low pressure oil flow into the oil reservoir below the push rod seat. Specifically, the invention provides in a mechanical tappet adapted for operative connection to a push rod for reciprocation within a crankcase, a tappet which comprises a body, an oil inlet hole in the body, an oil reservoir in the body, a push rod seat, means for supporting the seat within the body above the reservoir, and metering means for metering oil from the oil inlet hole through the seat and into the rod; the improvement comprising restricting means positioned between the inlet hole and the reservoir for restricting oil flow, the pressure drop across the restricting means exceeding that occuring anywhere else in the tappet.

This construction preferably includes locating the oil inlet hole above the support for the push rod seat and providing the proper diametral clearance between the push rod seat and that portion of the body in which the seat is located. This provides a metering and restricting means which provides oil under low pressure in the reservoir insuring controlled oil flow to the overhead oiling system.

Accordingly, it is an object of the invention to provide a metering mechanical tappet constructed in such a way as to control the flow of oil on the base circle.

It is a further object of the invention to provide a tappet of the above character which is capable of providing metered flow of oil without blockage due to impurities.

It is another object of the invention to provide a tappet of the above character which is inexpensive to manufacture and assemble.

Other objects and advantages will become apparent upon reference to the following drawings and detailed discussion.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary elevational view partially in section of a tappet constructed in accordance with the invention;

FIG. 2 is a bottom view of the push rod seat utilized in the device shown in FIG. 1;

FIG. 3 is a fragmentary partially sectioned elevational view illustrating an alternate embodiment of the invention; and

FIG. 4 is a bottom view of the push rod seat shown in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS This invention relates to an improved mechanical tappet l utilized in a conventional engine block having a crankcase 11 and a passageway 12 connecting the tappet to an oil gallery. The tappet conventionally seats a push rod 14 by means of a generally cylindrical push rod seat 16, the entire combination being reciprocated in a conventional fashion by a cam 18 on a cam shaft 20. The push rod seat 16 is positioned above an oil reservoir 24 by means of an annular shoulder 26 formed by an internal push rod seat cavity 28 which is larger in diameter than the diameter of the oil reservoir 24. In the device shown in FIG. I, the push rod seat 16 rests upon the shoulder 26. In one of my embodiments as illustrated by FIG. I, the metering of the oil into the push rod seat is accomplished by a predetermined diametral clearance formed by the diameter of the exterior wall 30 of the push rod seat and the diameter of the interior wall 32 forming the push rod seat cavity 28. This clearance and this clearance alone controls the rate of oil flow into the push rod 14 from the push rod seat 16 inasmuch as the central opening 34 in the push rod seat and the bottom opening 36 in the push rod are fonned with a considerably larger dimension than the diametral clearance. I have found that a clearance of 0.00l/0.0035 inch between the walls for a push rod seat having a diameter of 0.500/0.700 inch has worked satisfactorily.

Also, the push rod seat 16 is conventionally prevented from axial expulsion out of the tappet body by means of a retainer 40, the wall 32 of the cavity 28 having a groove 42 formed therein for holding the retainer snapped in place, thereby restraining the retainer from axially moving within the cavity 28.

In accordance with the invention, to restrict the oil flow coming out of the passageway 12 into the oil reservoir 24 to that the pressure drop prior to the entrance into the oil reservoir exceeds that occurring anywhere else in the tappet, (thereby insuring a low pressure supply of oil to the reservoir 24), the oil inlet hole 50 in the wall of the tappet 10 is located above the annular shoulder 26 so that oil must flow downwardly away from the push rod 14 through the diametral clearance described above in order to enter the oil reservoir 24. It will be readily appreciated that the low pressure oil in the reservoir 24 thus reduces the possibility of spurts of excess oil.

To insure that the push rod seat in contacting shoulder 26 does not shut off the flow of oil into the reservoir 24 after reaching the bottom of the diametral clearance, so-called nonmetering passageways 54 and 56 are formed extending from the exterior wall 30 of the push rod seat 16 radially inward to a point in communication with the reservoir 24. These passageways are called nonmetering because of their size in comparison to the diametral clearance. To insure that oil flow is not blocked due to the shifting of the push rod seat 16 to one side, these passageways 54 and 56, in addition to oil hole inlets 50 and 51, are positioned apart on the circumference of the push rod seat and push rod seat cavity 28 (see FIGS. 1 and 2).

Operation of the embodiment of FIGS. 1 and 2 should be quite evident. The oil from the gallery flowing under high pressure from passageway 12 enters oil inlet holes 50 and 51 from the recess 52. It is forced between the diametral clearance between push rod seat wall 30 and wall 32 of the push rod seat cavity 28. This diametral clearance provides a metering and restricting function. The oil flows downwardly to the shoulder 26 and then crosses through the nonmetering slots 54 and 56 at the lower surface of the push rod seat, filling the reservoir 24. The oil under low pressure made possible by the metering and restricting function of the diametral clearance, flows into the center push rod seat hole 34, through opening 36 of the push rod, and up the hollow push rod to the rocker arm (not shown).

FIGS. 3 and 4 illustrate another embodiment of the invention, wherein the metering is not accomplished by the diametral clearance of the exterior wall of the push rod seat within the cavity. Parts which are similar to those described in the previous embodiment bear the same reference numeral to which the distinguishing suffix a has been added. Thus, as shown in FIG. 3, a tappet 10a is operated by a cam 18a within a crankcase lla, the oil flowing from a passageway 12a to a central opening 340 in a push rod seat 16a and thence into the push rod 14a. Like the previous embodiment, the inlet hole 50a is located above the annular shoulder 260 formed by the cavity 28a whose diameter exceeds that of the bore 240. However, as distinguished from the embodiment of FIG. I, the

diameter of the exterior wall 30a of the push rod seat 16a is chosen to provide a diametral clearance without any metering or restricting function or effect.

Instead, the oil flows down past a nondiametral clearance and crosses through nonmetering slots to a metering means formed by the lower configuration of the push rod seat and a metering disc 80.

Specifically, disc 80 is positioned on the annular shoulder 26a and cooperates with a specially formed lower surface 82 of the push rod seat 16a in the following manner. That is, surface 82 is a land surface surrounding central opening 340 and shaped by a cylindrical valley or groove 84 (FIG. 4) concentrically positioned with respect to the central opening 34a. Still another groove or valley 86 is cut radially through the land surface 82 so that it extends from the central opening 340 to the valley 84. it is by means of the metering valley 86 that additional metering is provided from the oil in the valley 84 to the central opening 34a. To allow the oil to flow from the diametral clearance into the valley 84, two l80 opposed nonmetering slots 54a, 56a are provided on the circumference of the bottom surface of the push rod seat in a manner identical with the previous embodiment. The push rod seat 16a thus rests upon the disc 80 by means of the land surface 82, the disc in turn being supported by the annular shoulder 26a, so that the disc provides both a supporting function as well as a me tering function.

In this particular embodiment, it is necessary to bias the push rod seat 160 to prevent any axial movement which would cause separation of the seat from the disc 80. Thus, an annular flexible retainer ring 90 is snapped into position within the cavity 28a, the surface 92 of the ring bearing against the top surface of the push rod seat 16a. To restrain the retainer ring 90 from axial movement within the cavity 28a, a groove 94 is provided in the wall of the cavity 28a. Or, optionally, the groove 94 can be omitted so as to rely solely on the press fit of the retainer ring 90 within the cavity to prevent any axial movement. By these means, the push rod seat 16a is prevented from separating from the disc 80 such as under the conditions of lash.

The operation of this embodiment of FIGS. 3 and 4 is as follows: high pressure oil flows from passageways 120 into oil hole inlets 50a and 51a and down past the nonmetering diametral clearance between walls 30a and 32a. It then crosses through nonmetering slots 54a and 56a to the recessed circular area or valley 84 (FIG. 4). From thence it flows around to the valley or slot 86 into push rod seat opening or hole 34a. This tortuous route provides sufficient metering and restriction to insure controlled oil flow to the overhead oiling system.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. ln a mechanical tappet adapted to be operatively connected to a push rod for reciprocation within a crankcase, said tappet comprising a tappet body having an upper and lower cavity portion therein, an oil inlet hole means through the wall of said body and communicating with said cavity, a push rod seat positioned in said upper cavity portion, said push rod seat having an opening for supplying oil to a hollow push rod, support means for supporting said seat within said body above said lower cavity portion, said support means being fixed with relation to said tappet body, the improvement comprising: locating said oil inlet hole means above said support means; and means defining a constant restricted passageway between said oil inlet hole and said opening in said push rod seat for metering and restricting oil flow through said push rod seat opening.

2. The improved tappet as defined in claim 1, wherein said lower cavity portion defines an oil reservoir, and said means defining a restricted passageway includes a predetermined diametral clearance between the exterior wall of said seat and that portion of the interior wall of said cavity in which said seat is located, said diametral clearance providing a passageway between said inlet and said reservoir.

3. he improved tappet as defined ll'l claim 2, whereln a nonmetering passageway means is provided in conjunction with the said push rod seat and said means for supporting said push rod seat whereby oil flows therethrough into said reservoir from said diametral clearance.

4. The improved tappet as defined in claim 3, in which the nonmetering passageway means includes two nonmeten'ng passageways positioned 1 apart.

5. The improved tappet as defined in claim 1, wherein said means defining a restricted passageway includes a disc positioned on said seat support between said seat and said seat support, and a metering slot means is provided on the surface of said seat in contact with said disc.

6. The improved tappet as defined in claim 5, and further including at least on nonmetering passageway extending inwardly from said exterior seat wall to said metering slot.

7. The improved tappet as defined in claim 5, and further including biasing means for constantly biasing said seat surface against said disc to prevent separation, such as caused by lash, of said seat from said disc.

8. The improved tappet as defined in claim 7, wherein said biasing means includes a resilient retainer, and said cavity includes means for restraining said retainer from axial movement.

9. The improved tappet as defined in claim 8, wherein said restraining means includes a groove in said cavity interior wall into which said retainer is snapped, whereby said retainer prevents separation of said seat from said disc. 

1. In a mechanical tappet adapted to be operatively connected to a push rod for reciprocation within a crankcase, said tappet comprising a tappet body having an upper and lower cavity portion therein, an oil inlet hole means through the wall of said body and communicating with said cavity, a push rod seat positioned in said upper cavity portion, said push rod seat having an opening for supplying oil to a hollow push rod, support means for supporting said seat within said body above said lower cavity portion, said support means being fixed with relation to said tappet body, the improvement comprising: locating said oil inlet hole means above said support means; and means defining a constant restricted passageway between said oil inlet hole and said opening in said push rod seat for metering and restricting oil flow through said push rod seat opening.
 2. The improved tappet as defined in claim 1, wherein said lower cavity portion defines an oil reservoir, and said means defining a restricted passageway includes a predetermined diametral clearance between the exterior wall of said seat and that portion of the interior wall of said cavity in which said seat is located, said diametral clearance providing a passageway between said inlet and said reservoir.
 3. The improved tappet as defined in claim 2, wherein a nonmetering passageway means is provided in conjunction with the said push rod seat and said means for supporting said push rod seat whereby oil flows therethrough into said reservoir from said diametral clearance.
 4. The improved tappet as defined in claim 3, in which the nonmetering passageway means includes two nonmetering passageways positioned 180* apart.
 5. The improved tappet as defined in claim 1, wherein said means defining a restricted passageway includes a disc positioned on said seat support between said seat and said seat support, and a metering slot means is provided on the surface of said seat in contact with said disc.
 6. The improved tappet as defined in claim 5, and further including at least on nonmetering passageway extending inwardly from said exterior seat wall to said metering slot.
 7. The improved tappet as defined in claim 5, and further including biasing means for constantly biasing said seat surface against said disc to prevent separation, such as caused by lash, of said seat from said disc.
 8. The improved tappet as defined in claim 7, wherein said biasing means includes a resilient retainer, and said cavity includes means for restraining said retainer from axial movement.
 9. The improved tappet as defined in claim 8, wherein said restraining means includes a groove in said cavity interior wall into which said retainer is snapped, whereby said retainer prevents separation of said seat from said disc. 